Method for synthesizing flumioxazin

Abstract

The invention relates to a herbicide, in particular to a synthesis method of flumioxazin, which comprises the following steps: carrying out hydrogenation reduction reaction on 7-fluoro-6-nitro-1, 4-benzoxazine-3 (4H)-ketone in the presence of a solvent to generate 6-amino-7-fluoro-1, 4-benzoxazine-3 (4H)-ketone; then, the 6-amino-7-fluorine-4-propynyl-1, 4-benzoxazine-3 (4H)-ketone and a propynylation reagent are subjected to a propynylation reaction, and 6-amino-7-fluorine-4-propynyl-1, 4-benzoxazine-3 (4H)-ketone is generated; and carrying out amidation reaction on the flumioxazin and 3, 4, 5, 6-tetrahydrophthalic anhydride to generate the flumioxazin. The method provided by the invention is simple in post-treatment operation, convenient for industrial operation, low in three wastes, high in yield and few in impurities, and can effectively provide high-purity flumioxazin.

Description

Technical Field

[0001] The invention relates to a herbicide, in particular to a method for synthesizing fluazifop-butyl. Background Art

[0002] Fluazifop-butyl is an N-phenylphthalimide herbicide with excellent efficacy and inhibitory effect on protoporphyrinogen oxidase (PPO) in various weeds. It is an important product in "other PPO inhibitor herbicides". Due to its broad spectrum, high efficiency, easy degradation, strong selectivity, environmental friendliness and other characteristics, it meets the characteristics of "green pesticides", so fluazifop-butyl is widely used in agricultural production and has huge economic market value.

[0003] At present, there are many process routes reported for the synthesis of fluazifop-butyl, but the yields are not ideal. There are mainly the following methods:

[0004] Route 1: US4803270A discloses a route to obtain fluazifop-butyl using 1,5-dichloro-2,4-dinitrobenzene as a starting material through hydrolysis, fluorination, etherification, hydrogenation reduction ring closure, propynylation and condensation; and also discloses a route to obtain fluazifop-butyl using 1,5-difluoro-2,4-dinitrobenzene as a starting material through etherification, hydrogenation reduction ring closure, propynylation and condensation. In both routes, fluorination and nitration are difficult to control, with many side reactions and low yields.

[0005] Route 2: US4792605A discloses a method for synthesizing fluazifop-butyl using m-fluorophenol as a raw material through etherification, nitration, iron powder reduction ring closure, propynylation, and condensation with anhydride. m-fluorophenol in this route is expensive, and it is difficult to control the nitration, especially the ether bond is prone to breakage and oxidation during the nitration process. In addition, this route uses iron powder reduction, the yield is low, and the iron mud produced is difficult to handle.

[0006] Route 3: CN105837563A discloses a method of using 2,4-difluoronitrobenzene as a starting material, and obtaining the product of fluazifop-butyl through nitration, etherification, hydrogenation reduction ring closure, propynylation and condensation. The first step of nitration in this route is easy to generate trinitro compounds, the reaction temperature is high, the risk is high, and there are safety hazards in industrial scale-up production; the last condensation of this route uses acetic acid as a solvent, which is very easy to produce acetylated impurities, which are difficult to remove, affecting the yield and product quality.

[0007] The synthesis method of fluazifop-butyl needs to be further improved. Summary of the invention

[0008] The present invention aims to solve at least one of the above-mentioned problems in the prior art.

[0009] The invention provides a method for synthesizing fluazifop-butyl. The method has simple post-processing operation, is convenient for industrial operation, has low three wastes, high yield and few impurities, and can effectively provide high-purity fluazifop-butyl.

[0010] A method for synthesizing fluazifop-butyl comprises the following steps:

[0011] 1) subjecting 7-fluoro-6-nitro-1,4-benzoxazin-3(4H)-one to hydrogenation reduction in the presence of a solvent to generate 6-amino-7-fluoro-1,4-benzoxazin-3(4H)-one;

[0012] The solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone and 1,4-dioxane;

[0013] 2) subjecting the feed solution after the hydrogenation reduction reaction in step 1) (mainly a solution containing 6-amino-7-fluoro-1,4-benzoxazine-3(4H)-one) to a propynylation reaction with a propynylation agent to generate 6-amino-7-fluoro-4-propynyl-1,4-benzoxazine-3(4H)-one;

[0014] 3) subjecting the feed solution after the propynylation reaction in step 2) (mainly a solution containing 6-amino-7-fluoro-4-propynyl-1,4-benzoxazine-3(4H)-one) to an amidation reaction with 3,4,5,6-tetrahydrophthalic anhydride to generate fluazifop-propylamine.

[0015] CN105061416A discloses a method for preparing high-content fluazifop-butyl, wherein 6-amino-7-fluoro-4-propynyl-1,4-benzoxazine-3(4H)-one is contacted and reacted with 3,4,5,6-tetrahydrophthalic anhydride in a solvent in the presence of a catalyst; the catalyst is an alkaline nitrogen-containing organic matter or a mixture of an organic acid and an alkaline nitrogen-containing organic matter, and the solvent is a solvent capable of azeotropically removing water. The fluazifop-butyl product prepared by the method can have a yield of more than 90%, a purity of more than 99% by weight, and a content of organic impurities of less than 0.1% by weight. However, this method uses solid raw materials and has high requirements for raw materials. If the purity of 6-amino-7-fluoro-4-propynyl-1,4-benzoxazine-3(4H)-one and 3,4,5,6-tetrahydrophthalic anhydride is low, the impurity content of the fluazifop-butyl product will be increased, and the fluazifop-butyl product must be further purified, or the two raw materials must be pre-purified before feeding. In addition, the catalyst of this method uses alkaline nitrogen-containing organic matter or a mixture of organic acid and alkaline nitrogen-containing organic matter, the post-processing is cumbersome, and the catalyst is difficult to recover.

[0016] CN110669041A targets the raw material 3,4,5,6-tetrahydrophthalic anhydride with high content of phthalic anhydride and 2,3,4,5-tetrahydrophthalic anhydride, which can be directly fed without purification and contacted with unpurified 6-amino-7-fluoro-4-propynyl-1,4-benzoxazine-3(4H)-one to effectively avoid the formation of two difficult-to-remove impurities M354-Δ2 and M350, and control the content of these two impurities in the crude product of fluazifop-butyl to below 0.1%. This method requires pre-reaction of 3,4,5,6-tetrahydrophthalic anhydride with aqueous acetic acid; the method is slightly complicated; if the pre-reaction is not performed first, the content of the two difficult-to-purify impurities M354-Δ2 and M350 cannot be controlled.

[0017] The present invention has found that the same solvent is used in the above three-step reaction in the method of the present invention (see above for details). On the one hand, there is no need to separate the intermediate in each step of the reaction, and the reaction product (i.e., liquid material) can directly enter the subsequent step reaction, which is simple to post-process and suitable for industrial operation; on the other hand, the use of the same solvent in the three-step reaction can significantly improve the solvent recovery rate and reduce the recovery cost. The prior art requires concentration and distillation of solvent recovery after each step of the reaction. The method of the present invention only needs to distill the final reaction solution (i.e., the material after the reaction in step 3), which reduces the recovery cost.

[0018] However, when the reaction solvent is 1,2-dichloroethane, the pre-reaction dehydration cannot be achieved in the second step; when the reaction solvent is toluene, the raw materials cannot be completely dissolved. Therefore, these two solvents cannot be used in the first two steps of the reaction.

[0019] In the present invention, there is no particular limitation on the amount of the solvent used. Generally, the amount is sufficient to allow the reaction to proceed.

[0020] In some embodiments, in step 1), the volume ratio of the amount of 7-fluoro-6-nitro-1,4-benzoxazin-3(4H)-one to the solvent is 1 mol:(1.5-1.8)L.

[0021] Generally, the hydrogenation reduction reaction in step 1) can be carried out under conventional conditions in the art. For example, the reaction pressure can be 1.2-1.5 MPa, and can be 1.5 MPa; the reaction temperature can be 60-65° C., and the reaction time can be 6-8 h.

[0022] In some embodiments, the hydrogenation reduction reaction in step 1) is carried out in the presence of a first catalyst. Specifically, the first catalyst is at least one of Raney nickel and Pd / C (palladium on carbon), preferably Raney nickel. The amount of the first catalyst can be conventionally used in the art.

[0023] In some embodiments, the mass ratio of the amount of 7-fluoro-6-nitro-1,4-benzoxazin-3(4H)-one to the first catalyst is 1 mol:(20-25) g, optionally 1 mol:23 g.

[0024] In some embodiments, step 1) further comprises the step of filtering and recovering the catalyst after the hydrogenation reduction reaction. The recovered catalyst can be applied to the next batch.

[0025] In some embodiments, step 1) further comprises the step of filtering and recovering the catalyst after the hydrogenation reduction reaction, and then distilling the solvent from the obtained filtrate. Generally, 40-65% (e.g., by volume L) of the total amount of solvent can be distilled off, for example, 50%. The distilled solvent (after distillation to remove water) can be applied to the next batch.

[0026] In some embodiments, in step 2), the feed solution after the hydrogenation reduction reaction in step 1) for the propynylation reaction (mainly a solution containing 6-amino-7-fluoro-1,4-benzoxazine-3(4H)-one) does not contain or substantially does not contain the first catalyst.

[0027] In some embodiments, in step 2), the propynylation agent may be at least one of 3-chloropropyne and 3-bromopropyne, preferably 3-chloropropyne. The amount of the propylation agent used is such that the solution of 6-amino-7-fluoro-1,4-benzoxazin-3(4H)-one is sufficient for the propylation reaction.

[0028] In some embodiments, in step 2), the propynylation reaction can be carried out according to conventional conditions in the art.

[0029] In some embodiments, in step 2), the temperature of the propynylation reaction is 35-45°C.

[0030] In some embodiments, step 2) further comprises the steps of cooling (e.g., cooling to 0-5° C.) and filtering to remove salt after the propynylation reaction. After filtering to remove salt, a 6-amino-7-fluoro-4-propynyl-1,4-benzoxazin-3(4H)-one solution can be obtained.

[0031] In some embodiments, in step 2), before the propynylation reaction, the step of pre-reaction dehydration of the feed liquid after the hydrogenation reduction reaction in step 1) (mainly a solution containing 6-amino-7-fluoro-1,4-benzoxazine-3(4H)-one) is also included. Preferably, the water is substantially removed completely. Herein, substantially removing the water completely means controlling the water content in the feed liquid after the hydrogenation reduction reaction in step 1) (mainly a solution containing 6-amino-7-fluoro-1,4-benzoxazine-3(4H)-one) to ≤1%.

[0032] The study found that by adding a pre-reaction dehydration step in step 2), the hydrolysis impurity 2-(4-amino-5-fluoro-2-propyl-2-alkynylamino)phenoxy)acetic acid can be significantly reduced, and the product yield and purity can be improved.

[0033] In some embodiments, the pre-reaction dehydration is carried out in a reactor with a water separator and a reflux pipe.

[0034] Considering the influence of the equivalent water generated by the salt formation of 6-amino-7-fluoro-1,4-benzoxazine-3(4H)-one in the reaction on the reaction system, the present invention adopts a method of adding an alkali to perform pre-reaction dehydration and remove the generated equivalent water. The alkali is at least one of potassium hydroxide and sodium hydroxide, preferably potassium hydroxide. Studies have found that the advantage of using the method of adding an alkali (potassium hydroxide, sodium hydroxide) to perform pre-reaction dehydration is that the reaction yield can be increased while the propyne reaction temperature can be increased and the reaction time can be shortened.

[0035] In some embodiments, the molar ratio of the amount of 7-fluoro-6-nitro-1,4-benzoxazin-3(4H)-one to the molar ratio of the base is 1:(1.10-1.15), preferably 1.13.

[0036] In some embodiments, the pre-reaction dehydration time is 2-3 hours, such as 1 hour.

[0037] In some embodiments, the pre-reaction dehydration is carried out under negative pressure conditions; the negative pressure can be selected to be -0.085 to -0.095 MPa, for example -0.09 MPa.

[0038] In some embodiments, the pre-reaction dehydration is performed at a temperature of 50-60° C. (eg, 55° C.).

[0039] Generally, the amidation reaction in step 3) can be carried out under conventional conditions in the art. Fortunately, due to the use of the first two steps, the method of the present invention in step 3) does not need to pre-react 3,4,5,6-tetrahydrophthalic anhydride with aqueous acetic acid, which can effectively avoid the formation of two difficult-to-remove impurities M354-Δ2 and M350, and control the content of these two impurities in the crude fluazifop-butyl to be below 0.1%. In addition, since the first two steps of reaction are adopted, in step 3) of the method of the present invention, it is not necessary to control the purity of 6-amino-7-fluoro-4-propynyl-1,4-benzoxazine-3(4H)-one and 3,4,5,6-tetrahydrophthalic anhydride (i.e., it is not necessary to purify and pre-treat the two in advance), nor is it necessary to purify the product fluazifop-butyl in step 3), so that the yield of fluazifop-butyl (total yield of three steps) can reach more than 80%, the purity can reach more than 98.0%, and the impurity content is qualified; wherein, the content of M350 is reduced to less than 0.17%, and the content of M354-Δ2 is reduced to less than 0.18%.

[0040] In some embodiments, in step 3) the amidation reaction, the reaction temperature is 90-130° C., preferably 110-120° C.; the reaction time is 3-8 h, preferably 4-5 h.

[0041] In some embodiments, in step 3) the amidation reaction, the molar ratio of 6-amino-7-fluoro-4-propynyl-1,4-benzoxazin-3(4H)-one to 3,4,5,6-tetrahydrophthalic anhydride is 1:(1.03-1.08), preferably 1:1.05.

[0042] In some embodiments, step 3) of the amidation reaction further includes the step of adding a second catalyst. The second catalyst is at least one of the solid acid catalysts HND-8, HND-12, HND-31, HND-34, HND-580, HND-582, and HND-587, preferably HND-8. Optionally, the mass ratio of the amount of 6-amino-7-fluoro-4-propynyl-1,4-benzoxazine-3(4H)-one to the solid acid catalyst is 1 mol:(35-40) g, preferably 1 mol:38 g.

[0043] CN105061416A uses a basic nitrogen-containing organic compound or a mixture of an organic acid and a basic nitrogen-containing organic compound, and the post-processing is relatively cumbersome, and the catalyst is difficult to recover. The present invention uses a solid acid catalyst, which is easy to recover. In addition, the solid acid catalyst of the HND series used in the present invention has the characteristics of long service life, good thermal stability and mechanical stability, only simple filtration is required after the reaction, and they have a unique pore structure, which is conducive to the full contact of the reactants, can be reused, and can effectively reduce the cost of use.

[0044] In some embodiments, step 3) further includes the step of filtering and recovering the catalyst after the amidation reaction. The recovered catalyst can be applied to the next batch. The filtrate after the catalyst is recovered is cooled to precipitate a solid, which is filtered and dried to obtain the product fluazifop-butyl without further purification. The filtrate is further distilled and the solvent is recovered, which can be applied to step 1).

[0045] In some specific embodiments, the method for synthesizing fluazifop-butyl comprises the following steps:

[0046] 1) Synthesis of 6-amino-7-fluoro-1,4-benzoxazine-3(4H)-one: 7-fluoro-6-nitro-1,4-benzoxazine-3(4H)-one, organic solvent A and a first catalyst are added to a (high-pressure) reactor, and after inert gas replacement (for example, three times), hydrogen is introduced, and then the reaction is stirred under controlled pressure and temperature conditions until the reactor pressure no longer decreases; after cooling, opening the reactor, and drawing out the material, the catalyst is filtered and recovered, and a portion (for example, half of the amount) of the solvent is evaporated from the filtrate to obtain a 6-amino-7-fluoro-1,4-benzoxazine-3(4H)-one solution;

[0047] The recovered catalyst can be applied to the next batch;

[0048] 2) Synthesis of 6-amino-7-fluoro-4-propynyl-1,4-benzoxazine-3(4H)-one: Add the 6-amino-7-fluoro-1,4-benzoxazine-3(4H)-one solution obtained in step 1) together with a base into a reactor (with a water separator and a reflux tube), control the temperature I to 50-60° C., stir under negative pressure, perform pre-reaction dehydration, then control the temperature II to 35-45° C., dropwise add a propynylating agent within (1 h), cool to 0-5° C. after the reaction, filter and remove salt to obtain a 6-amino-7-fluoro-4-propynyl-1,4-benzoxazine-3(4H)-one solution;

[0049] 3) Synthesis of fluazifop-butyl: Add the 6-amino-7-fluoro-4-propynyl-1,4-benzoxazine-3(4H)-one solution obtained in step 2, 3,4,5,6-tetrahydrophthalic anhydride, and the second catalyst to the reactor, control the temperature, react under stirring until the reaction is completed, filter and recover the catalyst while hot (apply to the next batch), cool the filtrate I to precipitate solid, filter and dry to obtain the product fluazifop-butyl. Recover the catalyst (apply to the next batch); recover the solvent after distillation of the filtrate II and apply it to step 1).

[0050] The present invention also provides another method for synthesizing fluazifop-butyl, comprising the step of subjecting 6-amino-7-fluoro-4-propynyl-1,4-benzoxazine-3(4H)-one to an amidation reaction with 3,4,5,6-tetrahydrophthalic anhydride in the presence of a solvent to generate fluazifop-butyl; the solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, and 1,4-dioxane. Optionally, the amidation reaction uses at least one of solid acid catalysts HND-8, HND-12, HND-31, HND-34, HND-580, HND-582, and HND-587.

[0051] The synthesis method of fluazifop-butyl of the present invention greatly reduces the amount of three wastes. The prior art generates a large amount of waste water when separating the intermediates, which increases the cost of post-processing. The method of the present invention only has waste salt from step 2) and residual waste from the kettle after distillation in step 3), and the cost of three wastes treatment is greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 The figure is a schematic diagram of the operation flow of the method of the present invention. DETAILED DESCRIPTION

[0053] The present invention will be described in detail below with reference to preferred embodiments. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0054] The operation process of the following embodiments can be found in Figure 1 .

[0055] The following detection methods for fluazifop, impurities M350 and M354-Δ2:

[0056] Instruments and reagents: Agilent 1100 liquid chromatograph, DAD detector, acetonitrile (chromatographic grade), water (ultrapure water);

[0057] Operating conditions

[0058] Liquid chromatography column: XDB-C8, 4.0×150mm, 5micron;

[0059] Column temperature: 25°C;

[0060] Mobile Phase:

[0061] Time / min Acetonitrile% 0.5% (v) acetic acid water% 0 20 80 5 20 80 15 90 10

[0062]

[0063] The retention time of fluazifop-butyl is 11.94 min; the retention time of M350 is 10.30 min; the retention time of M354-△2 is 8.91 min.

[0064] The impurity M350 and isomer M354-△2 of fluazifop-butyl are shown below:

[0065]

[0066] Example 1

[0067] A method for preparing fluazifop-butyl comprises the following steps:

[0068] 1) Hydrogenation reduction reaction

[0069] Check the 2L autoclave equipped with stirring, thermocouple and hydrogenation device, and after confirming that everything is normal, add 7-fluoro-6-nitro-1,4-benzoxazine-3(4H)-one (140g), N,N-dimethylformamide (1.2L) and Raney nickel (15g) into the autoclave. After nitrogen replacement three times, hydrogen is introduced for the last time to fill the system, and then the reaction is stirred at 1.5MPa and 60-65℃ until the autoclave pressure no longer decreases. Cool down, open the autoclave, extract the material, filter and recover the catalyst for the next batch, and after 0.6L of N,N-dimethylformamide is evaporated from the filtrate, 6-amino-7-fluoro-1,4-benzoxazine-3(4H)-one solution is obtained.

[0070] The evaporated N,N-dimethylformamide can be recycled after being distilled to remove water.

[0071] 2) Propylation reaction

[0072] The 6-amino-7-fluoro-1,4-benzoxazine-3(4H)-one solution (690 g) obtained in step (1) and potassium hydroxide (46.5 g) are added to a reactor equipped with a water separator and a reflux pipe, and the temperature I is controlled to be 55° C., and the mixture is stirred under negative pressure to perform a pre-reaction dehydration until no water is separated; then the system is cooled, the temperature II is controlled to be 40° C., 3-chloropropyne is added dropwise within 1 hour, and the temperature is cooled to 0-5° C. after the reaction is completed, and the generated potassium chloride is filtered to obtain a 6-amino-7-fluoro-4-propynyl-1,4-benzoxazine-3(4H)-one solution. The potassium hydroxide is a tablet with a purity of 90%.

[0073] 3) Amidation reaction

[0074] The 6-amino-7-fluoro-4-propynyl-1,4-benzoxazine-3(4H)-one solution (710 g) obtained in step (2), 3,4,5,6-tetrahydrophthalic anhydride (110 g) and solid acid catalyst HND-8 (25 g) are added to a reactor, the temperature is controlled to be 110-120° C., and the reaction is carried out under stirring until the reaction is completed. The catalyst is filtered and recovered while hot and applied to the next batch. The filtrate I is cooled to precipitate a solid, which is filtered and dried to obtain the product fluazifop-butyl. The filtrate II is distilled and N,N-dimethylformamide is recovered and applied to step (1).

[0075] The fluazifop-butyl prepared in this example has a content of 98.1% and a yield (total yield of three steps) of 85%. The impurities are all qualified compared with the previous ones, among which the content of M350 is 0.12% and the content of M354-Δ2 is 0.18%, and no further purification is required.

[0076] Example 2

[0077] The difference between this embodiment and embodiment 1 is that in the hydrogenation reduction reaction in step 1), the solvent is N,N-dimethylacetamide, and the rest is the same as embodiment 1.

[0078] The fluazifop-butyl prepared in this example has a content of 98.0% and a yield (total yield of three steps) of 80%. The impurities are all qualified compared with the previous ones, among which the content of M350 is 0.14% and the content of M354-Δ2 is 0.15%, and no further purification is required.

[0079] Example 3

[0080] The difference between this embodiment and embodiment 1 is that: in the propynylation reaction in step 2), the propargyl reagent is 3-bromopropyne; in the amidation reaction in step 3), the solid acid catalyst is HND-12, and the rest is the same as embodiment 1.

[0081] The fluazifop-butyl prepared in this example has a content of 98.5% and a yield (total yield of three steps) of 84%. The impurities are all qualified compared with the previous ones, among which the content of M350 is 0.17% and the content of M354-Δ2 is 0.18%, and no further purification is required.

[0082] Comparative Example 1

[0083] The difference between this comparative example and Example 1 is that: in step 2), the step of adding potassium hydroxide for pre-reaction dehydration is omitted; the rest is the same as Example 1.

[0084] The detection results of the propynylation reaction products in step 2) of Examples 1-3 and Comparative Example 1 are shown in Table 1 below:

[0085] Table 1

[0086]

[0087] In Table 1, [a], [b], and [c] are the relative contents of the impurities 2-(4-amino-5-fluoro-2-propyl-2-alkynylamino)phenoxy)acetic acid, 6-amino-7-fluoro-1,4-benzoxazine-3(4H)-one, and 6-amino-7-fluoro-4-propynyl-1,4-benzoxazine-3(4H)-one in the propynylation reaction product (solution) of step 2, respectively (liquid phase normalized proportion, internal standard method); [d] and [e] are the actual contents (liquid phase, external standard method) and yields obtained by separating 6-amino-7-fluoro-4-propynyl-1,4-benzoxazine-3(4H)-one from the propynylation reaction product (solution) of step 2, respectively. / indicates that it was not detected.

[0088] The liquid phase detection method used is as follows:

[0089] Instruments and reagents:

[0090] Agilent 1200 liquid chromatograph, DAD detector, acetonitrile (chromatographic grade), water (ultrapure water); phosphoric acid (analytical grade);

[0091] Operating conditions

[0092] Liquid chromatography column: XDB-C18, 4.6×150mm, 5micron;

[0093] Column temperature: 25°C;

[0094] Mobile Phase:

[0095] Time / min Acetonitrile% Phosphoric acid water (pH = 3)% 0 20 80 5 20 80 15 90 10

[0096]

[0097] It can be seen from Table 1 that after adding pre-reaction dehydration in step 2), the reaction selectivity, reaction yield and product content are greatly improved.

[0098] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A method for synthesizing fluazifop-butyl, characterized in that: The steps include: 1) subjecting 7-fluoro-6-nitro-1,4-benzoxazin-3(4H)-one to hydrogenation reduction in the presence of a solvent to generate 6-amino-7-fluoro-1,4-benzoxazin-3(4H)-one; The solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone and 1,4-dioxane; 2) subjecting the feed liquid after the hydrogenation reduction reaction in step 1) to a propynylation reaction with a propynylation agent to generate 6-amino-7-fluoro-4-propynyl-1,4-benzoxazine-3(4H)-one; 3) subjecting the feed liquid after the propynylation reaction in step 2) to an amidation reaction with 3,4,5,6-tetrahydrophthalic anhydride to generate fluazifop-propylamine.

2. The method for synthesizing fluazifop-butyl according to claim 1, characterized in that: In step 1), the volume ratio of the amount of 7-fluoro-6-nitro-1,4-benzoxazin-3(4H)-one to the solvent is 1 mol:(1.5-1.8)L.

3. The method for synthesizing fluazifop-butyl according to claim 1 or 2, characterized in that: Step 1) The hydrogenation reduction reaction is carried out in the presence of a first catalyst; the first catalyst is at least one of Raney nickel and Pd / C; Optionally, the mass ratio of the amount of 7-fluoro-6-nitro-1,4-benzoxazine-3(4H)-one to the first catalyst is 1 mol:(20-25) g, optionally 1 mol:23 g.

4. The method for synthesizing fluazifop-butyl according to any one of claims 1 to 3, characterized in that: In step 2), the propynylating agent is at least one of 3-chloropropyne and 3-bromopropyne; Optionally, the temperature of the propynylation reaction is 35-45°C.

5. The method for synthesizing fluazifop-butyl according to any one of claims 1 to 4, characterized in that: In step 2), before the propynylation reaction, the process further comprises a step of pre-reaction dehydration of the feed liquid after the hydrogenation reduction reaction in step 1); preferably, the water is substantially completely removed.

6. The method for synthesizing fluazifop-butyl according to claim 5, characterized in that: The pre-reaction dehydration is carried out by adding alkali; the alkali can be at least one of potassium hydroxide and sodium hydroxide; Optionally, the molar ratio of the amount of 7-fluoro-6-nitro-1,4-benzoxazin-3(4H)-one to the amount of the base is 1:(1.10-1.15), preferably 1.

13.

7. The method for synthesizing fluazifop-butyl according to claim 5 or 6, characterized in that: The pre-reaction dehydration is carried out under negative pressure; the negative pressure may be -0.085 to -0.095 MPa, for example -0.09 MPa; and / or, The pre-reaction dehydration is carried out at a temperature of 50-60°C.

8. The method for synthesizing fluazifop-butyl according to any one of claims 1 to 7, characterized in that: In step 3) the amidation reaction, the reaction temperature is 90-130° C., preferably 110-120° C.; the reaction time is 3-8 h, preferably 4-5 h; and / or, In step 3) the amidation reaction, the molar ratio of 6-amino-7-fluoro-4-propynyl-1,4-benzoxazin-3(4H)-one to 3,4,5,6-tetrahydrophthalic anhydride is 1:(1.03-1.08), preferably 1:1.

05.

9. The method for synthesizing fluazifop-butyl according to any one of claims 1 to 8, characterized in that: Step 3) The amidation reaction further comprises the step of adding a second catalyst; the second catalyst is at least one of the solid acid catalysts HND-8, HND-12, HND-31, HND-34, HND-580, HND-582, and HND-587, preferably HND-8; Optionally, the mass ratio of the amount of 6-amino-7-fluoro-4-propynyl-1,4-benzoxazin-3(4H)-one to the solid acid catalyst is 1 mol:(35-40) g, preferably 1 mol:38 g.

10. A method for synthesizing fluazifop-butyl, characterized in that: The method comprises subjecting 6-amino-7-fluoro-4-propynyl-1,4-benzoxazin-3(4H)-one to an amidation reaction with 3,4,5,6-tetrahydrophthalic anhydride in the presence of a solvent to generate fluazifop-propyl; the solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone and 1,4-dioxane; Optionally, the amidation reaction uses at least one of the solid acid catalysts HND-8, HND-12, HND-31, HND-34, HND-580, HND-582, and HND-587.

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